When an image is output to peripheral edge portions of a recording medium (al so referred to as a sheet), recording material (such as toner or ink) spreads out of the image area to peripheral portions of the sheet, as shown in FIG. 4, which causes a problem of contaminating the hands of a user and other print sheets in taking out a stack of sheets or handling a file.
FIG. 4 shows an example of contamination of edge surfaces of sheets.
In order to avoid such toner contamination, there are offered methods (for example, refer to Patent Document 1: Japanese Patent Publication TOKKAI No. H07-239617) which bias, in the same polarity as transfer, a transfer entrance guide plate for guiding a sheet to the transfer area to keep toner away and control the timing of biasing, methods (for example, refer to Patent Document 2: Japanese Patent Publication TOKKAI No. H07-271256 and Patent Document 3: Japanese Patent Publication TOKKAI No. 2002-244462) which remove toner adhered to the back side surface of a sheet, and methods (for example, refer to Patent Document 3: Japanese Patent Publication TOKKAI No. 2002-244462) which arrange a suction fan between the transfer area and fixing to absorb spattering or floating toner.
However, just by the method which is a technology disclosed in above Patent Document 1 to prevent toner contamination of edge surfaces of a sheet by the timing of biasing a transfer entrance guide plate, it is difficult to remove toner having been adhered.
The technology disclosed in Patent Document 2 only removes toner contaminating the back side surface of a sheet, but does not disclose about contamination of edge surfaces. The technology disclosed in Patent Document 3 is effective for collecting toner spattering from a sheet, but is not capable of removing toner adhered to a sheet, and may degrade an unfixed image with a large air flow rate.
An object of the present invention is to provide an image forming apparatus having a cleaning device for preventing contamination by excess toner (or ink) adhered to edge surfaces of a sheet even when outputting an image to edge portions.